1. Field of the Invention
The invention relates in general to the field of food preparation ovens, and specifically to a gas xe2x80x9ctruexe2x80x9d convection oven.
2. Description of the Related Art
Convection ovens have long been popular in the cooking industry for both residential and commercial use. Typically, a gas convection oven involves a heat source disposed underneath the oven cavity, and a fan within the cooking cavity to circulate the hot air in the cooking cavity. This arrangement has the disadvantage that the air being blown through the fan is only as hot as the air within the oven cavity. Thus the heating of the food in the oven is uneven and much of the heat from the heat source is lost.
In order to improve the heating efficiency and increase oven temperatures, it was contemplated to provide a heat source in close proximity to the fan such that the air being moved by the fan is hotter than the air within the oven cavity. Thus food products within the oven are heated uniformly by air of a higher temperature, thus increasing heat transfer efficiency between the air and food products and reducing cooking times. This arrangement is typically termed xe2x80x9ctrue convectionxe2x80x9d in the cooking appliance industry. Essentially, the term xe2x80x9ctrue convectionxe2x80x9d refers to an oven in which a burner, or heat source is disposed in close proximity to the fan and that the air passing through the fan and into the oven cavity is at a higher temperature than the air within the oven, thus the heat is convectively transferred from the hot, moving air to the food products within the oven.
Such xe2x80x9ctruexe2x80x9d convection environments are typically created with an electric heat source disposed immediately in front of, behind, or surrounding the convection fan. This convection heat source is typically provided in addition to heat sources for standard non-convective baking. This has the result of significantly increasing the cost of the oven due to the fact that the oven must be adapted to operate multiple heat sources of various type and size. When the standard heat source is a gas burner or broiler, the oven must be adapted to operate with both gas and electrical power. Additionally, it is difficult to install a gas burner in close proximity to the fan, as the turbulence caused by the fan will greatly affect flame stability and emission. It has also been difficult to design a gas burner which can function in both fan-on and fan-off conditions.
It is therefore desirable to create a gas xe2x80x9ctrue convectionxe2x80x9d cooking environment in an oven without the necessity of multiple heat sources, while providing the ability to draw hot air from a heating source with stable combustion conditions.
Therefore an oven is described herein which is capable of producing a xe2x80x9ctrue convectionxe2x80x9d environment with a single gas burner disposed underneath the oven bottom in a combustion box, and a flue spout disposed at the rear of the oven and attached to a fan to draw hot air and flue products directly from the burner within the combustion box and blow them into the oven cavity.
Thus, one embodiment of an oven having preferred features and advantages includes an oven comprising an oven cavity defined by a plurality of side walls, a bottom wall, a top wall, a back wall, and a door. A fan compartment is disposed substantially centrally on the back wall, and is defined by a baffle plate spaced forwardly from the back wall, a plurality of rearward-extending flanges, and a portion of the back wall. A centrifugal fan is preferably disposed within the fan compartment, and the baffle plate preferably has a central fan-inlet portion. A combustion box having a front wall, a rear wall, a plurality of side walls and a bottom wall is preferably mounted to an underside of the oven bottom. A tube-type gas burner having a longitudinal axis perpendicular to the oven side walls is preferably disposed in a forward portion of the combustion box. A flue spout is preferably disposed between the baffle plate and the oven cavity, and is preferably adapted to join the fan compartment and the combustion box in fluid communication.
The baffle plate preferably comprises peripheral outlets. In one preferred embodiment, the combustion box bottom comprises a rearward, upward slope, the front side of the combustion box comprises a plurality of primary air inlet holes, and the bottom of the combustion box preferably comprises a plurality of secondary air inlet holes. The oven may include exhaust vents located substantially near the bottom of the back wall. Openings may be formed in the oven bottom to provide direct fluid communication between the oven cavity and the combustion box. In one embodiment, the flue spout comprises an upper portion which covers substantially the entire fan inlet. Alternatively, in another embodiment, the flue spout upper portion covers substantially half of the fan inlet portion of the baffle plate. The fan compartment may also comprise an opening in its top or other flange.
Another embodiment of an oven having preferred features and advantages includes an oven cavity defined by two upright side walls, a bottom, a top, a back wall, and a door, the bottom having openings joining the oven cavity and the combustion box in fluid communication. A baffle plate having a central fan inlet portion and peripheral fan outlet portions preferably forms the front of a fan compartment disposed substantially at the center of the back wall. The fan compartment is preferably defined by the baffle plate, a plurality of rearward-extending flanges, and a portion of the back wall. A centrifugal fan is disposed within the fan compartment. A combustion box having a front wall, a rear wall, a plurality of side walls and a bottom is preferably mounted substantially centrally to an underside of the oven bottom. A flue spout with a solid front wall is preferably disposed between the baffle plate and the oven cavity, and preferably joins the fan compartment and the combustion box in fluid communication. According to this embodiment, the fan inlet is preferably substantially entirely covered by the flue spout. A tube-type gas burner having a longitudinal axis perpendicular to the oven side walls, is disposed in the front of the combustion box.
Additionally, the combustion box bottom may comprise a rearward, upward slope, the front side of the combustion box may comprise a plurality of primary air inlet holes, and/or the bottom of the combustion box may comprise a plurality of primary air inlet holes. The combustion box bottom may additionally comprise a plurality of secondary air inlet holes. The oven may include exhaust vents located substantially near the bottom of the back wall. The oven top preferably does not have a fan compartment attached thereto. The fan compartment may also comprise an opening in its top or other flange.
According to another preferred embodiment, an oven having desired features and advantages may include an oven cavity defined by a plurality of walls, a bottom, a top wall, a back wall, and a door; a combustion box having a plurality of upright walls and a bottom wall, the box being mounted to an underside of the oven bottom; the oven bottom having openings joining the oven cavity and the combustion box in fluid communication; a baffle plate having a central fan inlet and peripheral fan outlets; a fan compartment disposed substantially centrally on the back wall, and defined by the baffle plate, a plurality of rearward-extending flanges, and a portion of the back wall; a centrifugal fan disposed within the fan compartment; a tube-type gas burner disposed substantially near and parallel to the front wall of the combustion box; and a flue spout having a front wall, a top wall, a plurality of rearward-extending sides, and a lower inlet portion, the inlet portion being substantially wider than the top wall, the flue spout being disposed between the baffle plate and the oven cavity such that the inlet portion extends into the combustion box, and the flue spout covers a portion of the fan inlet such that the flue spout is placed in fluid communication with the fan compartment.
Additionally, according to this embodiment, the fan inlet may be substantially entirely covered by the flue spout, and the flue spout may be adapted to allow only heated air from the combustion box to enter the fan inlet. Exhaust vents are preferably located substantially near the bottom of the back wall.
According to still another embodiment, a method of convectively cooking a food product comprises the steps of providing an oven having a cooking space, a combustion box disposed below the cooking space, a fan compartment disposed at the rear of the cooking space, and providing a flue spout disposed to join the combustion box, the fan compartment, and the cooking space in fluid communication; providing a fan in the fan compartment; providing a gas burner in a front portion of the combustion box; igniting the burner and heating air in the combustion box; and employing the fan to draw heated air directly from the gas burner in the combustion box through the flue spout, and blowing the heated air horizontally into the cooking space.
Alternatively, the method may include providing fluid communication between the cooking space and the fan compartment with intake holes, and using the fan to draw air from the cooking space into the fan compartment and mixing the cooking space air with the combustion box air.
In another embodiment, the method includes providing fluid communication between the cooking space and the fan compartment with intake holes in a wall of the fan compartment, and using the fan to draw air from the cooking space into the fan compartment and mixing the cooking space air with the combustion box air, and blowing the mixed air horizontally into the cooking space.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
All of these embodiments are intended to be within the scope of the present invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.